Economic Importance Of Protozoa - Harmful Protozoa
Protozoa are found almost everywhere, in water, in moist surface of the soil, in air and even within the bodies of other animals and plants. They exert far more influence on the worldly affairs. They are harmful as well as useful species.
Soil Protozoa: several species of Protozoa, present in large numbers in soil feed upon the nitrifying bacteria and thus decline their activity and consequently tend to decrease the amount of nitrogen given to the soil by the nitrifying bacteria.
Water pollution: The Protozoa of faecal origin are responsible for water contamination or pollution. Some free living Protozoa also pollute water by producing aromatic and oily secretions with objectionable odors which render water unfit for human consumption. Some bioluminescent dinoflagellates living in sea multiply extensively to turn the water red with their bodies. The phenomenon is known as blooming and is the cause of ‘red tides’ experienced in the sea. The red water often gives afoul and disagreeable small to the ocean water. Large concentrations of these flagellate Protozoans may even lead to destruction of fish and poisoning of edible mollusks such as clam, oysters, mussels etc. making them unfit for human consumption.
Pathogenic Protozoa: Protozoa causing diseases are called pathogenic Protozoa. They occur in all classes of Protozoa.
Pathogenic Sarcodines: There are two common genera which live in the intestine of man and other animals. Two species of Entamoeba cause serious dysentery in man and in reptiles.
Pathogenic flagellates: The parasitic flagellates include Leishmania, Trypanosoma, Histomonas, Trichomonas, and Giardia. Three different species of Leishmania severe disease in man. These are transmitted by sandflies of the genus phlebotomus. The parasitic species of Trypanosoma in mammals causes serious diseases. Different Trichomonas species cause vaginal Trichomoniasis in humans, cattle, doves, pigeon, turkeys and chickens. Giardia intestinalis causes Giardiasis in humans.
Pathogenic Sporozoans: This super class is exclusively of parasitic forms. Some genera like Plasmodium, Eimeria, Isospora and Babesia include pathogenic species. Four species of Plasmodium cause malaria in man. Different species of Plasmodium cause malaria in monkeys tree rats and jungle fowl. Pathogenic species of Eimeria causes coccidiosis in chickens, rabbits, dogs, cats, cattle, sheep and goats. One parasitic species of Isospora infect intestine of man, others infect cats and dogs. Babesia are intra-erythrocytic parasites of various vertebrates and causes lethal fevers, malignant jaundice and anaemia in horses, rodents, cat’s goats etc.
Pathogenic Ciliates: Balantidium coli is the only important intestinal parasite in man and also often found in frogs.